US8035369B2 - Method for detecting an isolated network - Google Patents

Method for detecting an isolated network Download PDF

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US8035369B2
US8035369B2 US12/157,281 US15728108A US8035369B2 US 8035369 B2 US8035369 B2 US 8035369B2 US 15728108 A US15728108 A US 15728108A US 8035369 B2 US8035369 B2 US 8035369B2
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frequency
set forth
inverter
mains
grid
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US20090027037A1 (en
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Michael Strnad
Neidhardt Bechtel
Christian Hardt
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SMA Solar Technology AG
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network

Definitions

  • the invention relates to a method for detecting an isolated network for an inverter carrying a converter voltage that is adapted for connection in parallel with a grid having a mains frequency and electric loads and that is decoupled from the grid by a choke.
  • a consumer generation system must detect a failure of the utility grid and then suspend operation. It is not allowed to continue feeding the grid since a person performing maintenance works at the utility grid may get injured if a grid portion has been disconnected but the consumer generation system is still working in this portion.
  • Known grid monitoring methods are divided into passive and active methods. Passive methods only evaluate the measured values of the (one or three phase) mains voltage and of the mains frequency. Active methods influence the grid through current or voltage distortions in such a manner that the mains parameters or the mains impedance may be inferred from the response. A current distortion yields a voltage response, a voltage distortion, a current response.
  • Methods for detecting isolated networks are known that rely on a periodical frequency change of the converter voltage.
  • the converter frequency is thereby slightly changed for part of a period, for a period or for a plurality of periods. This results in a phase difference between the converter voltage and the mains voltage for a corresponding transient current to flow. If the grid fails, the isolated network follows the frequency change. Through positive feedback the frequency drift may be accelerated and switch-off may be achieved by trespassing the frequency limit value.
  • the method however needs a lot of computing time since the impedances are calculated by means of complex algorithms (e.g., FFT).
  • complex algorithms e.g., FFT
  • Methods for detecting isolated networks are further known which rely on impressing a pulse-shaped test current. At certain time intervals, a pulse-shaped test current is impressed in proximity to the zero crossing of the mains voltage. If the zero crossing of the mains voltage of this test current is displaced beyond an adjustable limit, one assumes that the impedance has changed and that an isolated network has formed.
  • this object is achieved in that a test signal is superimposed upon the converter voltage at a test frequency the frequency of which is smaller than the mains frequency, the amplitude of the test signal being much smaller than the nominal voltage amplitude of the mains voltage on the one side but still just large enough on the other side for changes in reactive power to be detectable as a result of the test signal, a reactive power share being determined, which oscillates with the test frequency, this share not being allowed to fall below an imposed minimum for an isolated operation to be reliably excluded.
  • the invention relies on the observation that, in operation, the reactive power flow changes with the test frequency if the utility grid is stable. If the utility grid fails, the reactive power flow hardly changes by virtue of the test signal.
  • test signal is superimposed on the converter voltage at a frequency (test frequency) that is smaller than the mains frequency, its amplitude being small as compared to the mains voltage, the mains-side reactive power share oscillating together with the test frequency but still being detectable. This share is not allowed to fall below an imposed minimum for reliably excluding isolated operation.
  • the method of the invention offers the advantage that the additional energy expense is at its lowest. There is no or only a low additional component load. Also, the method does not make any noise; existing algorithms for calculating the reactive power may be used; additional energy consumption for providing an interruption-free current supply is minimal; displacements of the zero crossing, which are e.g., caused by centralized ripple control signals do not lead to unintended isolated network detections. Also, it is not necessary to analyze several frequencies in terms of computation. As a result, the computing expense is minimal.
  • the voltage amplitude of the test signal is smaller than 2% of the nominal voltage amplitude of the mains voltage.
  • the frequency of the test frequency is considerably smaller than the mains frequency, in particular if the frequency of the test signal amounts to 0.5 to 5 Hz. This frequency may be well filtered out because it is far from the mains frequency.
  • Another advantageous developed implementation of the invention is characterized by the fact that the share of the mains reactive power oscillating with the test frequency is filtered out with the help of at least one so-called generalized integrator.
  • Such type integrators operate reliably and are known for example from DE 199 49 997 A1.
  • an aperiodic quantity of the square-root extractor is compared with a threshold value in the evaluation unit and monitored to see whether the value for the aperiodic quantity falls below the threshold value, this lower value being indicative of isolated network formation so that the inverter is disconnected from the mains. Accordingly, the evaluation unit monitors whether the aperiodic quantity falls below a minimum threshold, this being indicative of isolated network formation.
  • the reactive power may be filtered using a Görtzel algorithm or by means of a Fourier transformation.
  • a suited FFT or a normal Fourier transformation may be utilized.
  • other suited methods for calculating a characteristic variable from a periodic signal may also be utilized.
  • Another very important preferred provision includes that the method of the invention may be used on a three-phase system.
  • the inverter is configured to be a battery inverter, the battery serving as an electric energy accumulator in the event of a power failure or to store excess energy of a photovoltaic generator.
  • the inverter may however also be configured to be a speed variable internal combustion engine, e.g., for a wind generator, a water power plant or a photovoltaic plant.
  • a speed variable internal combustion engine e.g., for a wind generator, a water power plant or a photovoltaic plant.
  • a good concept is to connect at least one second inverter connected to a generator, in particular to a photovoltaic generator, in parallel with the inverter.
  • electric loads may be fed either from the utility grid, from the photovoltaic generator and/or from the battery.
  • FIG. 1 shows an illustration of a circuit array with a battery inverter
  • FIG. 2 shows an illustration of an integrator circuit
  • FIG. 3 shows an illustration of a circuit array for isolated network detection
  • FIG. 4 shows a vector diagram with a converter voltage U s and a mains voltage U n .
  • FIG. 1 shows an illustration of a circuit array with a battery inverter 2 .
  • the circuit array constitutes a consumer generating system for electric energy. It not only includes the battery inverter 2 , to which there is connected a rechargeable battery 1 , but also a solar generator or a photovoltaic generator 8 with a second inverter 7 that is connected in parallel with the battery inverter.
  • the battery inverter 2 has a choke 3 by which it is connected in parallel with a grid 5 , a transfer contactor 4 being interposed therein between.
  • a wind power plant with PM generator, a speed variable internal combustion engine, a fuel cell or the like may be utilized. These are increasingly used for generating energy.
  • a consumer generation system must detect a failure of the utility grid and then stop operating. It is not allowed to continue feeding the grid as this might endanger a person performing maintenance work on the utility grid if a grid portion is disconnected whilst the consumer generation system continues operating in this portion.
  • the consumer generation system must be complemented with the battery-assisted additional inverter 2 or battery inverter 2 .
  • a method for isolated network detection is utilized for the inverter 2 carrying a converter voltage that operates in parallel with the grid 5 at a mains frequency of 50 or 60 Hz and is connectable to the electric loads 6 .
  • the inverter 2 is decoupled from the grid 5 through the choke 3 .
  • a test signal having a test frequency that is smaller than the mains frequency is superimposed on the converter voltage, the amplitude of the test signal being much smaller than the nominal voltage amplitude of the mains voltage on the one side but still just large enough on the other side for changes in reactive power to be detectable as a result of the test signal.
  • a reactive power share is thereby determined, and the inverter is disconnected from the mains if the value falls below a defined value. Through this disconnection from the mains, the loads 6 are no longer connected to the grid 5 .
  • the battery inverter 2 ensures the load supply upon power failure of the grid 5 even if the consumer generation system is not capable of delivering energy for the moment because of cloudy weather with low sun irradiation.
  • This battery inverter 2 is equipped with the transfer contactor by means of which the connection of the consumer generation system to the utility grid or to the grid 5 may be interrupted.
  • the consumer generation system consists of the solar inverter 7 , the photovoltaic generator 8 and the battery inverter 2 .
  • the battery 1 is connected to the grid 5 via the battery inverter and the decoupling choke 3 as well as via the transfer contactor 4 .
  • the loads 6 are supplied from the grid 5 or from the battery inverter 2 if the transfer contactor 4 is open.
  • the solar generator 8 may contribute to supply the loads 6 . If more solar energy is generated than needed by the load 6 , the battery may be charged through the battery inverter 2 or energy may be fed into the grid 5 .
  • the inverter 2 is therefore preferably configured to be a bidirectional inverter.
  • the converter voltage 11 , the mains current 12 and the mains voltage 13 are measured and supplied in digitized form to a suited digital computer (not shown), more specifically to a microprocessor.
  • the reactive power i.e., the mains frequency reactive power on the mains side, is preferably calculated also for other control functions. Accordingly, the reactive power is calculated at no additional expense.
  • the share of reactive power oscillating with the test frequency is filtered out with the help of what is referred to as a generalized integrator. Such type generalized integrators are discussed in closer detail in the document DE 199 49 997 A1.
  • FIG. 2 shows such a generalized integrator.
  • the integrator includes two subtraction members 31 and 32 , two amplifiers 33 and 35 and two integrators 34 and 36 .
  • the amplifiers 33 , 35 multiply the respective input signal by a circuit frequency to which the generalized integrator is tuned.
  • the circuit frequency is obtained from the test frequency multiplied by 2 ⁇ Pi (Hz).
  • the mains-side mains frequency reactive power serves as the input variable of the circuit shown.
  • the output y one obtains the reactive power share that oscillates with the test frequency.
  • the output x is the reactive power share displaced by 90° with respect to the output y that oscillates with the test frequency.
  • FIG. 3 shows a block diagram for detecting the formation of an isolated network.
  • An isolated network may be detected by an analogous circuit or through a microprocessor program. Therefore, FIG. 3 represents the complete algorithm needed to detect the formation of an isolated network.
  • the grid-side, mains-frequency reactive power serves as the input variable for the generalized integrator 21 .
  • Its output variable y serves as the input variable for the generalized integrator 22 , which generates the output signals x and y that are displaced 90° relative to each other.
  • These output signals are then squared in square members 23 and 24 and the outputs of the square members are added in an adder 25 the output variable of which is square rooted in a square-root extractor 26 and finally supplied to an evaluation unit 27 .
  • the evaluation unit 27 as well as the other members may be realized by a program of the microprocessor, meaning by software only.
  • the output of the square-root extractor 26 is an aperiodic quantity.
  • the evaluation 27 monitors this aperiodic quantity. If the aperiodic quantity falls below an imposed threshold, this means that an isolated network has formed because the grid-side reactive power oscillates very little or not at all with the test frequency.
  • FIG. 4 shows a voltage diagram. It serves to illustrate the following mathematical context.
  • U s is thereby a converter voltage and U n a mains voltage.
  • each inverter 2 comprising a decoupling choke 3 .
  • the mains voltage, the mains frequency, the inverter's active power and the inverter's reactive power are measured thereby.
  • the momentary mains voltage thereby serves as a base for computing the needed target value for the reactive power.
  • the reactive power is then set by a controller of the battery inverter according to this target value. If the voltage drops, the reactive power increases.
  • the momentary mains frequency thereby serves as a basis for computing the needed active power target value.
  • the active power is then set by the controller of the battery inverter 2 according to this target value. If the frequency drops, the active power increases.
  • a reactive power measurement already existing in this constellation in the inverter 2 is preferably utilized in the method of the invention to detect an isolated network.
  • the amplitude of the converter voltage is superimposed on the converter voltage with a sinusoid, the frequency of the superimposed voltage (test frequency) being much smaller than the mains frequency (about 1 to 2 Hz) and the voltage amplitude of the superimposed voltage being just high enough for the reaction to this change in voltage to be detected with sufficient accuracy (about 1% of the nominal voltage amplitude or less).
  • the reactive power flow is measured on the grid side. If the utility grid is stable, this reactive power flow changes with the test frequency. If the utility grid fails, the reactive power flow no longer varies or varies significantly less with the test frequency. This change is recorded as well as, by virtue of the change in the reactive power flow, the fact that the utility grid no longer operates. Then, the transfer contactor 4 must be opened.
  • the invention is not limited to this example; the reactive power with regards to the share that oscillates with the test frequency may also be filtered with other algorithms.
  • the method may also be used in three-phase systems. Each phase may be considered irrespective of the other phases.
  • the test signals need not be synchronized.
  • a voltage may be modulated such that the voltage signal is displaced 120° relative to the mains frequency in all the three phases.
  • a space vector signal of this three-phase system is thus obtained upon which a voltage having the test frequency is impressed.
  • the reactive power oscillating with the test frequency may then be calculated from the mains current converted into said space vector model and from the mains voltage converted into said space vector model.
  • test signals of the various converters are then synchronized via a suited data connection.
  • the reactive power that oscillates with the test frequency may be filtered using the Görtzel algorithm or a suited FFT or a normal Fourier transformation if a generalized integrator is not to be used.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Inverter Devices (AREA)
US12/157,281 2007-06-14 2008-06-09 Method for detecting an isolated network Active 2029-10-07 US8035369B2 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
EP07011655 2007-06-14
EP07011655.3 2007-06-14
EP07011655 2007-06-14
EP07013347 2007-07-07
EP07013347.5A EP2003759B1 (de) 2007-06-14 2007-07-07 Verfahren zur Inselnetzerkennung
EP07013347.5 2007-07-07

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RU169439U1 (ru) * 2016-12-26 2017-03-17 Евгений Борисович Колесников Измерительный преобразователь переменного напряжения в постоянное
RU2644612C1 (ru) * 2016-10-18 2018-02-13 Евгений Борисович Колесников Измерительный преобразователь переменного напряжения в постоянное

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WO2013008413A1 (ja) * 2011-07-08 2013-01-17 川崎重工業株式会社 複合発電システム向け電力変換装置
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DE102016116207A1 (de) * 2016-08-31 2018-03-01 Sma Solar Technology Ag Energieversorgungsanlage sowie Verfahren und Regelvorrichtung zur Regelung einer Energieversorgungsanlage
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US10305283B1 (en) * 2018-02-22 2019-05-28 General Electric Company Power angle feedforward signal for phase locked loop in wind turbine power systems
CN112345826B (zh) * 2020-10-23 2022-04-29 安徽大学 孤网失稳状态下频率和暂态谐波测量方法
DE102022104015B4 (de) 2022-02-21 2023-08-31 Sma Solar Technology Ag Inselnetzerkennung spannungseinprägender Wechselrichter und Wechselrichter

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5587662A (en) 1995-02-10 1996-12-24 North Carolina State University Method and apparatus for nondisruptively measuring line impedance at frequencies which are relatively close to the line frequency
DE19949997A1 (de) 1999-10-15 2001-06-07 Inst Solare Energieversorgungstechnik Iset Verfahren und Vorrichtung zur Bestimmung charakteristischer Grösse aus einem zeitlich periodischen Signal
US20030098671A1 (en) * 2001-11-26 2003-05-29 Visteon Global Technologies, Inc. Anti-islanding detection scheme for distributed power generation
EP1340988A2 (de) 2002-02-19 2003-09-03 Institut für Solaire Energieversorgungstechnik (ISET) Verein an der Universität Gesamthochschule Kassel e.V. Verfahren und Vorrichtung zur Messung der Impedanz eines elektrischen Energieversorgungsnetzes
US20030165036A1 (en) 2002-01-16 2003-09-04 Ballard Power Systems Corporation Anti-islanding device and method for grid connected inverters using random noise injection
US6810339B2 (en) * 1997-11-24 2004-10-26 Plug Power, Inc. Anti-islanding method and apparatus for distributed power generation
US6850074B2 (en) * 2002-08-05 2005-02-01 Encorp, Inc. System and method for island detection
US6933714B2 (en) * 2002-02-19 2005-08-23 Institut Fuer Solare Energieversorgungs-Technik (Iset) Verein An Der Universitaet Gesamthochschule Kassel E.V. Method and apparatus for measuring the impedance of an electrical energy supply system
US7015597B2 (en) * 2003-09-11 2006-03-21 Square D Company Power regulator for power inverter
US7106564B2 (en) * 2002-01-16 2006-09-12 Ballard Power Systems Corporation Devices and methods for detecting islanding operation of a static power source
EP1764894A1 (de) 2005-09-19 2007-03-21 ABB Schweiz AG Verfahren zur Erkennung des Inselbetriebs eines dezentralen Energieerzeugers
US7376491B2 (en) * 2005-10-26 2008-05-20 General Electric Company Detection of islanding in power grids

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5587662A (en) 1995-02-10 1996-12-24 North Carolina State University Method and apparatus for nondisruptively measuring line impedance at frequencies which are relatively close to the line frequency
US6810339B2 (en) * 1997-11-24 2004-10-26 Plug Power, Inc. Anti-islanding method and apparatus for distributed power generation
DE19949997A1 (de) 1999-10-15 2001-06-07 Inst Solare Energieversorgungstechnik Iset Verfahren und Vorrichtung zur Bestimmung charakteristischer Grösse aus einem zeitlich periodischen Signal
US20030098671A1 (en) * 2001-11-26 2003-05-29 Visteon Global Technologies, Inc. Anti-islanding detection scheme for distributed power generation
US7106564B2 (en) * 2002-01-16 2006-09-12 Ballard Power Systems Corporation Devices and methods for detecting islanding operation of a static power source
US20030165036A1 (en) 2002-01-16 2003-09-04 Ballard Power Systems Corporation Anti-islanding device and method for grid connected inverters using random noise injection
EP1340988A2 (de) 2002-02-19 2003-09-03 Institut für Solaire Energieversorgungstechnik (ISET) Verein an der Universität Gesamthochschule Kassel e.V. Verfahren und Vorrichtung zur Messung der Impedanz eines elektrischen Energieversorgungsnetzes
US6933714B2 (en) * 2002-02-19 2005-08-23 Institut Fuer Solare Energieversorgungs-Technik (Iset) Verein An Der Universitaet Gesamthochschule Kassel E.V. Method and apparatus for measuring the impedance of an electrical energy supply system
US6850074B2 (en) * 2002-08-05 2005-02-01 Encorp, Inc. System and method for island detection
US7015597B2 (en) * 2003-09-11 2006-03-21 Square D Company Power regulator for power inverter
EP1764894A1 (de) 2005-09-19 2007-03-21 ABB Schweiz AG Verfahren zur Erkennung des Inselbetriebs eines dezentralen Energieerzeugers
US20080204044A1 (en) 2005-09-19 2008-08-28 Abb Schweiz Ag Method for detecting islanding operation of a distributed generator
US7376491B2 (en) * 2005-10-26 2008-05-20 General Electric Company Detection of islanding in power grids

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Jeraputra C., et al. "Development of a Robust Anti-Islanding Algorithm for Utility Interconnection of Distributed Fuel Cell Powered Generation." IEEE Transactions on Power Electronics, vol. 19, No. 5, Sep. 2004. 8 Pages.
Search Report for Application No. EP 07013347 Dated Oct. 17, 2008. 1 page.

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2644612C1 (ru) * 2016-10-18 2018-02-13 Евгений Борисович Колесников Измерительный преобразователь переменного напряжения в постоянное
RU169439U1 (ru) * 2016-12-26 2017-03-17 Евгений Борисович Колесников Измерительный преобразователь переменного напряжения в постоянное

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US20090027037A1 (en) 2009-01-29
EP2003759B1 (de) 2020-03-04

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